Apparatus are already known which comprise a fixed roller and a movable roller disposed in opposed relation to the fixed roller and movable toward and away therefrom for correcting the deviation of a travelling fabric by nipping the fabric with the two rollers when necessary.
With such a known deviation correcting apparatus, the movable roller is held away from the fixed roller by the action of a spring. When the selvage of a travelling fabric for which the apparatus is provided deviates toward the center line of the path of travel of the fabric, the movable roller is forced toward the fixed roller by a push rod on a diaphragm cylinder to nip the selvage with the two rollers for the correction of the deviation.
However, since the rollers are adapted to nip the selvage by the pressure of fluid supplied to the diaphragm cylinder, the nipping action invariably involves a time delay corresponding to the time taken for the supply of the fluid. Thus the selvage is actually nipped some time after the moment when it must be nipped. The delay of timing therefore substantially impairs the accuracy of deviation correction.